The invention pertains to a protective housing for optical equipment, especially for video surveillance cameras, with a tubular housing shell, which can be slid back and forth in a telescoping manner with respect to a housing carrier, which can be mounted in a fixed position. The housing shell and the equipment carrier are connected to each other by a sliding guide piece, which forms a pivot bearing after the housing shell has been pulled out as far as it can go, so that the shell can be pivoted downward around the end of the equipment carrier.
Protective housings of this kind serve to protect the optical equipment installed in them against mechanical effects, including those associated with sabotage, and also, when the protective housing is mounted outdoors, against weather-related influences. For this purpose, the protective housing is sealed at the forward end, i.e., in the "viewing direction" of the optical unit, by a window with a frame-shaped window flange; it is closed off at the rear by a rear wall, which usually holds the electrical devices such as cable inlets and leadthroughs. As a rule, the orientations of protective housings of this type can also be adjusted. They can also be mounted on an adjustable bracket or a so-called "tilt-and-swivel head" which can be motor-driven around two perpendicular axes, so that the housing can be moved into various positions. A considerable amount of installation work is required, however, both to install the protective housing on its bracket and also to install the optical equipment and the associated electrical and electronic devices in the housing.
Protective housings are therefore already known, in which the housing shell can be flipped open along two parting lines with axes which are parallel to each other. This leads, however, to sealing problems at the two parting lines mentioned and also at the joints which are present between the flip-up housing part and the two walls, i.e., the window wall and the rear wall.
As a result, it has long been standard practice to use a housing shell which consists of a piece of extruded material with a tubular profile, which already contains essentially all the necessary fastening and guide elements such as screw holes, mounting and stiffening ribs, and guide grooves for the sliding connection with the equipment carrier. In housing shells of this type, a smooth separating cut is sufficient to produce satisfactory sealing surfaces as required for the window wall and the rear wall. On the other hand, a housing shell sealed on all sides again leads to problems with the installation of the internal parts. Therefore, protective housings have also become known in which, after the screw joint holding the housing shell to the rear wall has been unfastened, the housing shell can be pulled out like a telescope from the equipment carrier with the internal parts.
EP-B1 No. 285,922 discloses two embodiments of a protective housing of the general type described above. In one case, the equipment carrier consists of a single profiled rail, connected to the rear wall; after the housing shell has been pushed on, this rail and the video camera are both inside the housing. The attachment occurs in this case by way of the rear wall. In the other case, the equipment carrier consists of two profiled rails, which can pivot with respect to each other. After the shell has been pushed into position, the upper rail is inside the housing shell, while the other rail, i.e., the lower one, winds up underneath the housing shell. In both cases, the end of the equipment carrier facing away from the rear wall is provided with a rigidly attached angle piece, at the end of which two laterally projecting cylindrical projections are provided, which engage in corresponding guide grooves, one of which is on top of the housing floor and the other on the bottom of the housing floor. The housing shell has a stop, which comes to rest against this angle piece when the shell has been moved out as far as it can go. In this position, it is possible to flip the housing shell downward around the cylindrical projections of the angle piece, so that the housing shell hangs down from the forward end of the equipment carrier. During the installation work, however, the now upward-pointing rear end of the housing shell is in the way, especially since the sliding guide piece has an angular shape. This means that the rear end of the shell still projects upward to a significant extent beyond the plane of the lower rail part of the equipment carrier, i.e., all the way up to a point in front of the upper rail part of the equipment carrier. This interferes considerably with the installation work on the front end of the equipment carrier, as part of which it may also be necessary to attach a heating element for the housing window, for example, and to wire this element to a power source. In the second embodiment, the lower rail part of the equipment carrier makes it possible to attach the unit in an adjustable manner to a bracket or to a tilt-and-swivel head.
Of particular importance, however, are the optical problems. The optical axis usually points at a certain downward angle, because protective housings of this type are usually mounted at a height where they are out of reach of people. Because the optical equipment usually includes a wide-angle lens or a wide-angle zoom lens, the optical system cannot be adjusted if the housing shell is suspended in the known manner like a pendulum, because the rear end of the shell cuts off a large part of the angular field. In addition, the housing shell is also provided with a protective roof, the rear end of which extends backward at least about 5 cm beyond the end of the housing shell, so that the rear wall of the housing is also offered protection by this roof. The rear wall of the housing extends for a considerable distance in the direction of the optical axis. The projecting part of the protective roof cuts off even more of the angular field and therefore creates considerable interference. Now, although appropriate longitudinal guides are provided so that the protective roof can be slid back along the housing shell, it is extremely difficult to accomplish this sliding action, because the roof may not be allowed to move unintentionally. Furthermore, the housing shell is provided with a protective coating such as with an anodized layer or a layer of resin, which would be damaged by a sliding movement of this kind. Such damage would lead not only to an unattractive appearance but also to the premature corrosion of the housing shell.